NCERT Class 6th Science Chapter 7 Motion and Measurement of Distances Question Answers

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NCERT Class 6th Science Chapter 7 Motion and Measurement of Distances Question Answers

1. Give two examples each, of modes of transport used on land, water, and air.

Ans. 

Land:

• Car: A common mode of land transport used for personal and public commuting.
• Bicycle: A manually powered vehicle often used for short-distance travel on land.

Water:

• Boat: A vessel used to travel across rivers, lakes, and seas.
• Ship: A large watercraft designed for transporting goods and passengers over long distances on oceans.

Air:

• Aeroplane: An aircraft used for long-distance travel and transportation of goods across countries.
• Helicopter: A type of aircraft that can take off and land vertically, used for short-distance travel, rescue missions, and accessing remote areas.

2. Fill in the blanks:

(i) One metre is 100 cm.

(ii) Five kilometres is 5000 m.

(iii) Motion of a child on a swing is periodic.

(iv) Motion of the needle of a sewing machine is periodic.

(v) Motion of the wheel of a bicycle is circular.

3. Why can a pace or a footstep not be used as a standard unit of length?

Ans.

A pace or footstep cannot be used as a standard unit of length because it varies from person to person. Different individuals have different stride lengths, which makes it an inconsistent and unreliable unit of measurement. Standard units like the metre are universally accepted and ensure uniformity and accuracy in measurement across the world.

4. Arrange the following lengths in their increasing magnitude:

1 millimetre, 1 centimetre, 1 metre, 1 kilometre.

Ans.

Arranged order: 1 millimetre < 1 centimetre < 1 metre < 1 kilometre

5. The height of a person is 1.65 m. Express it in cm and mm.

Ans.

• In centimetres (cm):

  $$\mathrm{<br>}$$

• In millimetres (mm):

  $$\mathrm{<br>}$$

So, the height of the person is 165 cm or 1650 mm.

6. The distance between Radha's home and her school is 3250 m. Express this distance in km.

Ans.

To convert metres into kilometres:

$$1\text{km}=1000\text{m}$$
$$3250\text{m}=\frac{3250}{1000}\text{km}=3.25\text{km}$$

So, the distance between Radha's home and her school is 3.25 km.

7. While measuring the length of a knitting needle, the reading of the scale at one end is 3.0 cm and at the other end is 33.1 cm. What is the length of the needle?

Ans.

To find the length of the needle, subtract the reading at the start from the reading at the end:

$$\text{Length of the needle}=33.1\text{cm}-3.0\text{cm}=30.1\text{cm}$$

So, the length of the knitting needle is 30.1 cm.

8. Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.

Ans.

Similarities:

• Both the wheel of the bicycle and the blades of the ceiling fan exhibit circular motion around a fixed axis.
• When in motion, both rotate continuously as long as the bicycle is moving or the fan is switched on.

Differences:

• Source of Motion: The bicycle’s wheel rotates due to the force applied by the rider, whereas the ceiling fan blades rotate due to the electric motor.
• Functionality: The bicycle’s wheel moves the entire vehicle forward, exhibiting rectilinear motion in addition to circular motion, while the fan blades remain stationary in one place and only provide air circulation.

9. Why would you not like to use a measuring tape made of an elastic material like rubber to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with such a tape?

Ans.

A measuring tape made of elastic material like rubber would stretch when pulled, leading to inaccurate measurements. This elasticity would vary based on how much force is applied while measuring, resulting in different measurements for the same distance. If you measure a distance using such a tape, it would be difficult to provide an accurate and consistent measurement to someone else, as the tape would likely stretch differently each time, causing confusion and errors.

10. Give two examples of periodic motion.

Ans.

• Pendulum of a clock: The pendulum swings back and forth at regular intervals, making it an example of periodic motion.
• Heartbeat: The rhythmic beating of the heart at regular intervals is also an example of periodic motion.